Power transformer for industrial heating apparatus



Jan. 24, 1967 P. N. soRI-:NSEN

POWER TRANSFORMER FOR INDUSTRIAL HEATING APPARATUS Filed April 17, v1964 5 Sheets-Sissi l II HH I.

Jan. 24, i967 P. N. SORENSEN POWER TRANSFORMER FOR INDUSTRIAL HEATING APPARATUS 5 Sheets-Sheet 2 Filed April i7, 1964 INVENTOR. PHILLIPS N. SORENSEN QQ-2 A TORNEYS Jan. 24, 1967 P. N. SORENSEN 3,300,614

POWER TRANSFORMER FOR I NDUSTRIAL HEATING APPARATUS I5 Sheets-Sheet 5 Filed April '17, 1964 FIG. 9

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INVENTOR PHILLIPS N. SORENSEN United States Patent 3,300,614 POWER TRANSFORMER FOR INDUSTRIAL HEATING APPARATUS Phillips N. Sorensen, Bedford, Ohio, assignor to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 17, 1964, Ser. No. 360,514 8 Claims. (Cl. 219-10.43)

This invention pertains to the art of industrial heatin-g apparatus and more particularly to a power transformer for such an apparatus.

The invention is particularly applicable to an induction heating apparatus for surface hardening the bearing pins of a crankshaft and it will be discussed with particular reference thereto; however, it will be appreciated that the invention has much broader applications and may be used in other industrial heating apparatus of the type used for surface hardening Ior heating of numerous workpieces.

Generally, the present invention pertains to surface hardening or heating of a workpiece having an eccentric surface, such as the bearing pins of a crankshaft, as the workpiece is being rotated about an axis. As the 'workpiece is rotated, the eccentric surface not only rotates; but, it also translates back and forth with respect'to the rotational axis. Thus, a heating element, hereinafter referred to as an inductor, which is adapted to ride along the eccentric surface to heat the surface progressively, must be so mounted to allow relatively free reciprocal and oscillatory movement with respect to the workpiece axis. In other words, the inductor must be mounted to float in various directions so that the inductor remains in uniform spaced relationship with the eccentric surface being heated as the workpiece is rotated. This required compound reciprocal and oscillatory movement for the inductor has presented various electrical and mechanical problems which 'will be hereinafter described in detail.

An inductor for heating the eccentric surface of a workpiece, such as the surface of a bearing pin on a crankshaft, is electrically coupled onto the secondary Winding of a power transformer and, in the past, this secondary winding was fixed with respect to the remander of the transformer structure. The floating, compound reciprocal and oscillatory movement of the inductor was permitted by mounting the inductor on a pantograph lever system so that the inductor could ride in a controlled manner on the eccentric surface of the bearing pin. Such an arrangement required flexible, water cooled cables or flexible bus bars for electrically coupling the inductor onto the secondary of the power transformer. The flexible coupling between the transformer secondary and the floating inductor caused power losses, increased maintenance problems and increased costs.

In an attempt to eliminate the requirement for flexible electrical couplings or connections between the secondary winding of the power transformer and the floating inductor, some industrial heating apparatus provided a power transformer whi-ch was movable as a unit with respect to the rotatable axis of the workpiece. This was unsatisfactory because such mounting arrangements for the transformer were cumbersome and exceedingly expensive to manufacture and maintain. Also, by movably mounting the power transformer, the input leads to the transformer were continuously flexed during operation of the heating installation. Thus, these leads would sometimes fail during operation.

These and other disadvantages of the prior industrial heating apparatus are completely overcome by the present invention which is directed t-oward a power transformer for an industrial heating apparatus which transformer is so constructed to allow movement of a floating inductor without flexible electrical connectors or couplings between the transformer and the inductor and without movably mounting the whole transformer with respect to the rotational axis of the workpiece.

In accordance with the present invention there is provided an improvement in a power transformer comprising a primary winding, a secondary winding, and a stationary core having a leg `and inductively coupled to both of the windings. This improvement comprises providing the secondary winding with an elongated central opening, a wear resistant guide means mounted on the core leg and surrounding the secondary winding, the guide means contacting the opening and being contoured to allow reciprocal and oscillating movement of the secondary winding with respect to the core leg.

By this arrangement, the inductor can be rigidly connected onto the secondary winding of the transformer and the transformer, as a unit, can be fixedly mounted with respect to the rotational axis of the workpiece. Floating movement of the inductor along the eccentric surface of the workpiece is allowed by the movement of the secondary within the transformer itself.

In accordance 'with a further aspect of the present invention, there is provided an improvement in an apparatus for heating the eccentric Isurface of a rotating Workpiece, the apparatus including a heating element riding along the eccentric surface, a power transformer with a stationary ferro-magnetic core, a primary winding and a secondary winding and means for mechanically coupling the secondary winding onto the heating element. The improvement, in accordance with this invention, includes the provision of the mechanical coupling means as a substantially rigid coupling between the secondary winding and the heating element and the provision of means for allowing reciprocation and oscillation of the secondary 'winding of the transformer with respect to the stationary core.

The phrase rotational and translational movement as used in defining the movement of the surface being heated indicates that the surface is ecenctric or is eccentrically mounted with respect to the rotatable axis of the workpiece so that an inductor or other heating element riding along the surface at a somewhat fixed relationship with the rotational axis must reciprocate axially with respect to the rotational axis and, to a somewhat lesser extent, must oscillate with respect to the axis. In other words the inductor or other heating element must be mounted to float in a path including compound reciprocation and oscillation.

The primary object of the present invention is the provision of a heating apparatus for heating a workpiece su'rface having rotational and translational movement with respect to the rotational axis of the workpiece which apparatus includes a movable heating element and a relatively fixed power transformer without requiring complicated flexible connectors between the element and the transformer.

Another object of the present invention is the provision of a heating apparatus for a workpiece surface having coupled directly onto the heating element of the apparatus and means for allowing reciprocal and oscil- 4latory movement of the secondary winding and the heating element with respect tothe remainder of the transformer.

These and other objects and advantages will become apparent from the following description used to illustrate 'the preferred embodiment of the invention as read in connection with the accompanying drawing in which:

FIGURE 1 is a partial, somewhat schematic, isometric view illustrating the preferred embodiment of the present invention;

FIGURE 2 is a cross-sectional, somewhat schematic, enlarged side elevational view showing the preferred embodiment of the present invention as illustrated in FIG- URE 1 with the secondary winding in two separate posiltions;

FIGURE 3 is a cross-sectional view taken generally along line 3--3 of FIGURE 2;

FIGURE 4 is a partial, top elevational view illustrat- Ving, somewhat schematically, the inductor illustrated in FIGURES l and 2;

FIGURE 5 is a partial, somewhat schematic, isometric view illustrating a modification of the preferred embodiment shown in FIGURES 1-4;

FIGURE 6 is a cross-sectional, somewhat schematic view illustrating a further modication of the preferred embodiment shown in FIGURES 1 4;

FIGURE 7 is a cross-sectional view taken generally along line 7-7 of FIGURE 6;

FIGURE 8 is a partial, somewhat schematic, isometric view illustrating a further modification of the preferred embodiment shown in FIGURES 1 4;

FIGURE 9 is a cross-sectional view taken generally along line 9 9 of FIGURE 8; and,

FIGURE l0 is a cross-sectional view taken generally along line 11i-10 of FIGURE 8.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGURE l shows, somewhat schematically, an industrial heating apparatus A adapted to heat workpiece B, which is in the form of a conventional crankshaft rotatably mounted on axis x. More specifically, the apparatus A is adapted to inductively heat the eccentric surface 1,0 of bearing pin 12 which surface is radially offset from the workpiece rotational axis x. Referring more specically to FIGURE 2, as the workpiece B is rotated about axis x, the pin 12, and thus surface 10, orbits about axis x so that the surface has combined rotational and translational movement with respect to the axis x. Such combined movement of the eccentric surface 10 as it rotates presents certain problems in heating the surface 10 with an inductor of the type to be hereinafter described in detail. This same combined rotational and translational movement of the heated surface is found when the lobe of a cam is being rotated about an eccentric axis. Accordingly, it is appreciated that the particular movement of the surface 10 could be varied without departing from the intended spirit and scope of the invention as long as the surface 10 is not coaxial with respect to its rotational axis. In other words, the surface 10 is eccentric with respect to the axis x so that a heating element in contact with or floating near the surface will have at least reciprocal movement with respe-ct to axis x and, in many cases, oscillatory movement with respect to this axis.

In accordance with the illustrated embodiment of the present invention, the eccentric surface 10 is adapted to be heated by an inductor Ztl shown in FIGURES 1, 2 and 4 which inductor includes a loop 22 and leads 24, 26. As pin 12 rotates about axis x, the inductor guide pins 28 ride along the surface to maintain the inductor spaced slightly from the surface 10 so that the inductor can inductively heat the surface. A spring means or other appropriate arrangement (not shown) is used to bias the inductor 20 in contact with surface 10. During the rotation of the pin 12, the inductor 2t) rides along the surface 10; therefore, the inductor oscillates along the path `a and translates or reciprocates along the path b as is illustrated in FIGURE 2. Accordingly, the inductor has oscillatory and reciprocal movement as the pin 12 rotates and translates with respect to axis x. It is appreciated that the pins 28 are only representative in nature and various other arrangements can be provided for maintaining the inductor 2t) spaced only slightly from the surface 10. It is important to realize that the inductor 20 cannot be xed with respect to the axis x if a close spacing from the surface 10 is to be maintained. The inductor actually floats in a path which is the resultant movement of the Icompound reciprocal and oscillatory movement of inductor 20.

The primary aspect of the present invention is the provision of a power transformer, designated as transformer 30, for powering the inductor 20 by a high frequency current supplied to the transformer from a power source, such as a generator or an oscillator, which power source has been eliminated from the disclosure for the purposes of simplicity. In accordance with the preferred embodiment of the present invention, the transformer 30 includes a stationary ferro-magnetic core 32, best shown in FIGURE 3, with an inner leg 34. On the upper and lower edges of the inner leg 34, there are provided guide blocks 40, 42 formed from a wear resistant, electrical insulation material and having spaced end plates 44. Positioned between the end plates of each block 40, 42 there are provided a plurality of arcuately shaped grooves 46 which define yupwardly extending arcuate ribs 48 having a center of curvature near the geometric center of leg 34. Any number of grooves and ribs can be provided without departing from the intended spirit and scope of the present invention.

As so far described, the transformer 30 Ihas a stationary ferro-magnetic core and two spaced guide blocks. In grooves 46, and between ribs 48, there is interwoven a primary winding 50 which is connected onto the output of the power source for driving the transformer 30 with line or high frequency alternating current. The primary winding may have any number of turns and it is within the contemplation of the present invention to provide' more than one turn in each of the grooves 46. After positioning the primary winding around the inner leg 34 and blocks 40, 42, a secondary winding 60 is positioned between the plates 44 and above the arcuate ribsv 48, as is shown in FIGURES l-3. In accordance with the illustrated embodiment of the present invention, the secondary winding takes the form of a single turn having an inner guide surface 62 which is somewhat elliptical in shape so that it can be positioned around the ribs 48 without contacting the primary winding 50. As is illustrated in the drawings, the plates -44 and 4arcuately shaped ribs 48 form a receiving structure for the secondary winding 60 so that the secondary winding can be shifted back and forth along the blocks 40, 42 and rotated slightly around the arcuate ribs 48. This construction allows oscillation and reciprocation of the secondary winding 60 with respect to the ferro-magnetic core 32. It is appreciated that the winding 60 could have more than one turn without departing from the intended spirit and scope of the invention. In FIGURE 5, a multi-turn secondary coil 60a is shown. In accordance with the illustrated embodiment as shown in FIGURES 1-4, the single turn secondary winding 60 terminates in a pair of spaced leads 64, 66 which leads are rigidly connected onto leads 24, 26, respectively, so that the ourrent flowing within the secondary winding 60 ows around loop- 22 of the inductor 20.

In practice, the transformer 30 is lixedly positioned with respect to the axis x and the secondary winding 60 reciprocates and translates with respect to the remainder of the transformer as the oating inductor 20 oscillates and translates upon orbital movement of the pin 12 around axis x. The length of the leads 64, 66 determines the amount of movement which can be allowed by the inductor 20 without the secondary winding contacting the core 32 of the transformer. The phrase, reciprocation and oscillation, as applied to the movement of the inductor 20, is actually applicable to the movement f the secondary winding 60 with respect ofthe core 32.

From this description of the preferred embodiment of the present invention, it is appreciated that the inductor can be directly coupled onto the power leads 64, 66 of the transformer 30 without requiring flexible electrical connections or couplings and without requiring movement of the transformer as a unit. This is a substantial advance in the art of industrial heaters for eccentric surfaces such as those found in heat treating the bearing pin surfaces of a crankshaft.

It is within the contemplation of the present invention to provide the primary winding with an inner shape somewhat similar to the inner shape of surface 62 so that both the primary and secondary windings can translate and oscillate with respect to the inner leg 34 of the transformer core 32. Such an embodiment is illustrated in FIGURE 6 wherein a transformer 70 includes a single turn secondary winding 72 with an oblong central opening 72a yand a multi-turn primary winding 74 with an oblong central opening 74a, similar in shape to opening 72a. The turns of winding 74 are received in grooves 46 so that this secondary winding can oscillate and shift on the blocks 40, 42. In this illustrated embodiment, the turns of the primary winding 74 are connected onto the inner surface of winding 72 by a layer of insulation material '76. (See FIGURE 7.)

Referring now to FIGURES 8, 9 and l0, there is illustr'ated @a further embodiment of the present invention wherein transformer 80 includes guide blocks 82, 84 with spaced end plates 86 and annular grooves 88 and 90. The blocks 82, 84 are formed from non-magnetic, high electrical resistivity material having high wear resistant qualities. A multi-turn secondary winding 100 having an oblong central opening 102 is positioned with the turns thereof being received in grooves 88. The grooves 90, which are axially aligned with grooves 88, receive the individual turns of a multi-turn primary winding 104 so that the primary and secondary windings are interleaved with each other. The embodiments of the present invention shown in FIGURES 5-10 function in a manner similar to the operation of the preferred embodiment shown in FIGURES 1-4.

rIhe present invention has been described in connection with various structural embodiments; however, structural changes may be made in these embodiments without departing from the intended spirit :and scope of the present invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In an apparatus for heating the eccentric surface of a rotating workpiece, the apparatus including a heating element riding along said eccentrc surface, a power transformer with a stationary, ferro-magnetic core, a primary winding and a secondary winding and first means for mechanically coupling said secondary winding to said heating element, the improvement comprising: said first means being a substantially rigid coupling between said secondary winding and said element and second means for allowing .at least reciprocation of said secondary winding with respect to said stationary core, said core including a leg, said primary winding being wound onto said leg, said secondary winding having an elongated central opening, and said second means including electrically insulated guide means on Said leg, said guide means receivable in said elongated opening of said secondary winding to allow reciprocation of said secondary winding on said guide means and with respect to said leg.

2. The improvement as defined in claim 1 wherein said guide means includes spaced grooves and said primary winding being wound into said grooves and around said leg.

3. The improvement as defined in claim 2 wherein said secondary winding is a multi-turn winding and said guide means includes a second set of spaced grooves with said turn of said secondary winding being movably received in said second set of grooves.

4. The improvement as defined in claim 1 wherein said guide means has spaced plates and an arcuate intermediate surface for defining a channel for movably supporting said secondary winding with respect to said core.

5. The improvement as defined in claim 1 wherein said secondary winding is a single turn winding.

6. In an apparatus for heating the eccentric surface of a rotating workpiece, the apparatus including a heating element riding along said eccentric surface, a power transformer with a stationary, ferro-magnetic core, a primary winding and a secondary winding and first means for mechanically coupling said secondary winding to said heating element, the improvement :comprising: said first means 'being a substantially rigid coupling ybetween said secondary winding and said element, second means for allowing at least reciprocation of said secondary winding with respect to said stationary core, a third means for allowing reciprocation of said primary winding with respect to said stationary core and fourth means for securing said primary winding onto said secondary winding.

7. In an apparatus for heating the eccentric surface of a rotating workpiece, the apparatus including a heating element riding along said eccentric surface, a power transformed with a stationary, ferro-magnetic core, a primary winding and a secondary winding and first means for mechanically coupling said secondary Winding to said heating element, the improvement comprising: said first means being a substantially rigid coupling between said secondary winding and said element, second means for allowing at least reciprocation of said secondary winding with respect to said stationary core and said heating element Ibeing an inductor and including means for maintalnmg said inductor in spaced relationship with said eccentric surface. 8. In a power transformer comprising a primary wind- 1ng, a secondary winding and a stationary core having a leg and inductively coupled to yboth of said windings, the lmprovement comprising: said secondary winding having an elongated central opening, a wear resistant guide means mounted on said leg and surrounded by said secondary w1nd1ng, said guide means contacting said opening and contoured to allow reciprocal and oscillating movement of said secondary winding with respect to said leg.

References Cited by the Examiner UNITED STATES PATENTS 1,413,053 4/1922 onstad 219-116 2,175,039 10/1939 souiiary 336-117 2,677,744 5/1954 Eahrenbach 336-117 2,922,026 1/1960 Hauptmann 219-116 FOREIGN PATENTS 650,184 2/1951 Great Britain.

RICHARD M. WOOD, Primary Examiner. L. H. BENDER, Assistant Examiner. 

8. IN A POWER TRANSFORMER COMPRISING A PRIMARY WINDING, A SECONDARY WINDING AND A STATIONARY CORE HAVING A LEG AND INDUCTIVELY COUPLED TO BOTH OF SAID WINDINGS, THE IMPROVEMENT COMPRISING: SAID SECONDARY WINDING HAVING AN ELONGATED CENTRAL OPENING, A WEAR RESISTANT GUIDE MEANS MOUNTED ON SAID LEG AND SURROUNDED BY SAID SECONDARY WINDING, SAID GUIDE MEANS CONTACTING SAID OPENING AND CONTOURED TO ALLOW RECIPROCAL AND OSCILLATING MOVEMENT OF SAID SECONDARY WINDING WITH RESPECT TO SAID LEG. 